[New-bugs-announce] [issue24421] Race condition compiling Modules/_math.c

[Martin Panter]

New submission from Martin Panter:

Once or twice I have had the math or cmath modules fail to build. There seems to be a race condition, because the _math.c file seems to be compiled twice, once for each module. Attached is a GCC wrapper that should help reproduce this fairly consistently. First, build Python normally:

$ ./configure
$ make -j2

Then force Modules/_math.c to be recompiled using my wrapper script to amplify the race condition:

$ touch Modules/_math.c
$ rm build/temp.linux-x86_64-3.6/media/disk/home/proj/python/cpython/Modules/_math.o
$ make -j2 CC=./slow-cc.py
running build
running build_ext
building 'cmath' extension
compiling for  cmath
./slow-cc.py [. . .]/Modules/cmathmodule.o
building 'math' extension
./slow-cc.py [. . .]/Modules/mathmodule.o
./slow-cc.py -fPIC -Wno-unused-result -Wsign-compare -Wunreachable-code -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -Werror=declaration-after-statement -I./Include -I. -IInclude -I/usr/local/include -I/media/disk/home/proj/python/cpython/Include -I/media/disk/home/proj/python/cpython -c /media/disk/home/proj/python/cpython/Modules/_math.c -o build/temp.linux-x86_64-3.6/media/disk/home/proj/python/cpython/Modules/_math.o
INITIAL COMPILE
./slow-cc.py -fPIC -Wno-unused-result -Wsign-compare -Wunreachable-code -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -Werror=declaration-after-statement -I./Include -I. -IInclude -I/usr/local/include -I/media/disk/home/proj/python/cpython/Include -I/media/disk/home/proj/python/cpython -c /media/disk/home/proj/python/cpython/Modules/_math.c -o build/temp.linux-x86_64-3.6/media/disk/home/proj/python/cpython/Modules/_math.o
RECOMPILE
RECOMPIILE TRUNCATING
INITIAL COMPILE FINISHED
./slow-cc.py -shared build/temp.linux-x86_64-3.6/media/disk/home/proj/python/cpython/Modules/mathmodule.o build/temp.linux-x86_64-3.6/media/disk/home/proj/python/cpython/Modules/_math.o -L/usr/local/lib -lm -o build/lib.linux-x86_64-3.6/math.cpython-36m-x86_64-linux-gnu.so
build/temp.linux-x86_64-3.6/media/disk/home/proj/python/cpython/Modules/_math.o: file not recognized: File truncated
collect2: error: ld returned 1 exit status
RECOMPILE FINISHED
./slow-cc.py -shared build/temp.linux-x86_64-3.6/media/disk/home/proj/python/cpython/Modules/cmathmodule.o build/temp.linux-x86_64-3.6/media/disk/home/proj/python/cpython/Modules/_math.o -L/usr/local/lib -lm -o build/lib.linux-x86_64-3.6/cmath.cpython-36m-x86_64-linux-gnu.so

Failed to build these modules:
math

----------
components: Build
files: slow-cc.py
messages: 245121
nosy: vadmium
priority: normal
severity: normal
status: open
title: Race condition compiling Modules/_math.c
type: behavior
Added file: http://bugs.python.org/file39672/slow-cc.py

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue24421>
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